650

THEORY AND PRACTICE OF ENGINEERING.

Book If.

Pcroxidt of Potassium : —

Potassium - I 40 62*4

Oxygen - - - 3 - 24 27.6

1 64 1000

Potassium combines with chlorine, iodine, bromine, hydrogen, and nitric acid to formNitrate of Potassa .— Saltpetre is an abundant mineral production , being found in manysoils, and particularly in old plaster rubbish, which sometimes, after washing, affords 5 percent, of this product; it is also found in situations where animal or vegetable matter hasbeen left in a putrefied state in contact with calcareous soils. Upon newly-built walls itsometimes shows itself, and is the result probably of the mortar containing hair, or otheranimal matter. Mortar made of lime, wood-ashes, and cow-dung produces in a short time

efflorescent nitre.

Oxvgen

- 6

48

47*10

Nitrogen

- 1

14

12*75

Potassium -

- 1

40

39*15

1

102

100*00

Gunpowder is a mixture of nitre,

sulphur, and charcoal in the following proportions : —

Common.

Shooting

Shooting.

Miners’

Powder.

Powder.

Saltpetre -

75

78

76

65

Charcoal -

12*5

12

- 15

15

Sulphur -

12*5

10

9

20

Potassium unites with sulphur, selenium, carbon, cyanogen, and boron.

Sodium is soft and malleable, and its globules may be welded together by pressure; incolour it resembles silver, but soon has its lustre changed by exposure to the air ; it fusesat 190°, and becomes volatile at a white heat; its specific gravity is 0*9343 ; when throwninto water hydrogen is given out, and the metal rapidly oxidises.

Sodium and Oxygen. — Soda.

Sodium

.

- 1

-

24

- 75

Oxygen

-

- 1

-

8

25

1

32

100

Peroxide of Sodiutn.

Sodium

.

- 1

-

24

66*7

Oxygen

-

- M

-

12

33*3

i

36

100*0

Chloride of Sodium .— Common salt exists as a fossil, and is found abundantly in solution.It is taken up nearly in the same quantities both by hot and cold water; in solutionit deposits crystals during evaporation, though it does not do so by cooling; 100 parts ofwater at 58° dissolve 36 of salt.

Common Salt is the source of soda, muriatic acid, and chlorine.

Sodium

.

- 1

.

24

40

Chlorine

-

-

- 1

-

36

60

1

60

100

Chloride of Soda is a powerful bleaching agent; when exposed to the air it absorbs car-bonic acid, and evolves chlorine, which occasions it to be used as a disinfectant.

Soda and Nitric Acid .— Nitrate of soda resembles common nitre ; it is found native inPeru , forming a stratum of many miles in extent, covered with clay and alluvium.

Soda

- 1

-

32

37*2

Nitric acid -

- 1

-

54

62*8

1

86

* 1000

Sulphuret of Sodium is composed of

Sodium

- 1

-

24

60

Sulphur

- 1

-

16

40

1

40

100